1. Field of the Invention
This invention relates to stabilized aqueous microemulsions, and, more particularly, to a method of chemically and physically stabilizing aqueous microemulsions containing a water-insoluble active ingredient which normally is subject to hydrolysis under basic conditions, or phase separation in a conventionally buffered acid medium.
2. Description of the Prior Art
Microemulsions are oil-in-water or water-in-oil, clear, thermodynamically stable dispersions of two or more immiscible liquids wherein the dispersed phase consists of small droplets or micelles with diameters in the range of about 10 to 100 millimicrons. Aqueous microemulsion compositions are used to conveniently disperse active ingredients such as agriculturally active chemicals which are substantially insoluble in water. However, often aqueous microemulsions are observed to be unstable hydrolysis of the active ingredient and/or leakage of the active ingredient resulting in precipitation or crystallization in the water phase. For example, carbamates, esters, amides, phosphate esters and thiophosphates esters such as hydramethylnon, Carbaryl, and the like, are known to hydrolyze in water under basic conditions.
Accordingly, it is an object of this invention to provide a chemically and physically stabilized aqueous microemulsion of an active ingredient subject to hydrolysis and/or precipitation.
Another object of this invention is to provide a method of stabilizing aqueous microemulsions against hydrolysis and/or precipitation of a water-insoluble, agriculturally active ingredient therein.
These and other objects and features of the invention will be made apparent from the following description thereof.